Prior FNST Studies and
Perspective on FNST Pathway
Mohamed Abdou
With major input from many experts
and colleagues over many years
FNST/PFC/Materials/FNSF Meeting, UCLA, August 2-6, 2010
Fusion Nuclear Science and Technology (FNST)
FNST is the science, engineering, technology and materials
for the fusion nuclear components that
generate, control and utilize neutrons, energetic particles & tritium.
Inside the Vacuum Vessel
“Reactor Core”:
 Plasma Facing Components
divertor, limiter and nuclear aspects of
plasma heating/fueling
 Blanket (with first wall)
 Vacuum Vessel & Shield
Other Systems / Components affected
by the Nuclear Environment:




Tritium Fuel Cycle
Instrumentation & Control Systems
Remote Maintenance Components
Heat Transport & Power Conversion Systems
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
Extensive FNST Studies over the past 25 years
included Technical Planning and Development Pathway
• Started with FINESSE (1983-87), evolved in IEA study (1994-96), and improved
in FNST community efforts the past several years.
• Involved fusion scientists, engineers (blanket, PFC, PMI, Materials, Tritium,
Safety), and plasma physicists .
• STRONG participation of experts in Technology development from Aerospace
and Fission industries.
• Very strong international participation.
• Over 200 man-year of efforts domestically and internationally.
• Developed processes for “Experiment Planning” based on ROLLBACK
Approach and utilized experience from other technologies.
• A study (2005-2007) to develop a technical plan and cost estimate for US ITER
TBM provided 1-understanding of the detailed R&D requirements (specific
tasks, cost, and time) and 2- insights into the practical and complex aspects
of preparing to place a test module and conduct experiments in the fusion
nuclear environment.
• Technical Reports and Journal Publications on website: www.fusion.ucla.edu
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST Studies Developed a PROCESS for Technical Planning Using
Rollback from Power Plants/DEMO and Analogy to Other Technologies
NUCLEAR FUSION, Vol.27, No.4 (1987)
EXPERIMENT PLANNING
FINESSE PROCESS For Experiment Planning
Is a Key Element of Technology
Development
Vision for Power Plants
Experience from
Other Technologies
Proposed Application
of a Scientific Principle
Conceptual Designs
promising designs
Characterize Issues
Quantify Experimental Needs
Experiment Planning
test plan
R & D Implementation
Commercial Product
FINESSE
Scope
Programmatic Guidance
promising design
concepts
Evaluate Facilities
Existing
New
Develop Test Plan
Role, Timing, Features of Major Experiments, Facilities
• Considered issues before experiments and experiments before facilities
• The idea of FNSF emerged from the last step of “Develop Test Plan”
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
How To Select “Promising Designs for Technical Planning”?
• FNST studies utilized vision of reactors for major parameters (wall load, plasma operating
mode, etc.) and overall configuration features.
• FNST studies concluded it could not just use designs of nuclear components from reactor
studies (because point designs make one specific choice to explore it).
• FNST studies selected and developed designs best suited for R&D strategy.
– e.g. Blanket comparison and selection study (BCSS) selected two classes of concepts:
Liquid Breeders and Solid Breeders as the basis for R&D planning. (Reason: both
classes have feasibility issues, can not select before testing in the fusion
environment)
– e.g. unrealistic assumption: tritium fractional burnup in the plasma.
Engineering Scaling for Experiments Must Be Based on Power Plant
Parameters (not on DEMO)
• Engineering scaling is the process to develop meaningful tests at experimental conditions
and parameters less than those in a reactor.
• DEMO fusion power is smaller than in power plants because of cost considerations.
Therefore, wall load in DEMO is lower than in power plant.
• e.g. Power Reactors: 3-4 MW/m2
DEMO: 2-2.3
FNSF: 1-1.5
Experiments in FNSF must be designed to show nuclear components can extrapolate
to power reactor. Hence engineering scaling in FNSF should be based on 3-4 MW/m2
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
Principal Requirements for a Fusion Energy System
1. Confined and Controlled
Burning Plasma (feasibility)
2. Tritium Fuel Self-Sufficiency
(feasibility)
3. Efficient Heat Extraction and
Conversion (feasibility)
4. Reliable System Operation
(feasibility/attractiveness)
5. Safe and Environmentally
Advantageous
(feasibility/attractiveness)
Fusion Nuclear Science and
Technology plays the KEY role
The challenge is to meet these
Requirements SIMULTANEOUSLY
Besides plasma confinement, the overall goal for fusion development should be:
“demonstrate tritium self sufficiency while simultaneously extracting high
temperature heat in a safe, reliable, maintainable and practical system.”
6
Top-Level Technical Issues for FNST (set 1 of 2)
(Details of these issues published in many papers by many authors, Last update: December 2009)
Tritium
1. “Phase Space” of practical plasma, nuclear, material, and technological
conditions in which tritium self sufficiency can be achieved
2. Tritium extraction, inventory, and control in solid/liquid breeders and blanket,
PFC, fuel injection and processing, and heat extraction systems
Fluid-Material Interactions
3. MHD Thermofluid phenomena and impact on transport processes in
electrically-conducting liquid coolants/breeders
4. Interfacial phenomena, chemistry, compatibility, surface erosion and
corrosion
Materials Interactions and Response
5. Structural materials performance and mechanical integrity under the effect of
radiation and thermo-mechanical loadings in blanket/PFC
6. Functional materials property changes and performance under irradiation
and high temperature and stress gradients (including HHF armor, ceramic breeders, beryllium
multipliers, flow channel inserts, electric and thermal insulators, tritium permeation and corrosion barriers, etc.)
7. Fabrication and joining of structural and functional materials
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
7
Top-Level Technical Issues for FNST (set 2 of 2)
Plasma-Material Interactions
8. Plasma-surface interactions, recycling, erosion/redeposition, vacuum
pumping
9. Bulk interactions between plasma operation and blanket and PFC systems,
electromagnetic coupling, and off-normal events
Reliability, Availability, Maintainability (RAMI)
10. Failure modes, effects, and rates in blankets and PFC’s in the integrated
fusion environment
11. System configuration and remote maintenance with acceptable machine
down time
All issues are strongly interconnected:
– they span requirements
– they span components
– they span many technical disciplines of science & engineering
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
8
Science-Based Framework for FNST R&D involves modeling
and experiments in non-fusion and fusion facilities
Theory/Modeling/Database
Basic
Separate
Effects
Property
Measurement
Multiple
Interactions
Phenomena Exploration
Non-Fusion Facilities
(non neutron test stands,
fission reactors and accelerator-based neutron
sources, plasma physics devices)
Experiments in non-fusion facilities are
essential and are prerequisites
Design Codes, Predictive Cap.
Partially
Integrated
Integrated
Component
•Fusion Env. Exploration Design
•Concept Screening
•Performance Verification
Verification &
Reliability Data
Testing in Fusion Facilities is
NECESSARY to uncover new
phenomena, validate the science,
establish engineering feasibility,
and develop components
Testing in Fusion Facilities
9
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST Studies Detailed the Types of Experiments in Non-Fusion Facilities
Example of Figures
from NUCLEAR
FUSION, Vol.27, No.4
(1987)
Solid Breeders
Liquid Breeders
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST Studies Defined in Detail
the Types of Experiments in Non-Fusion Facilities (continued)
Example of Figures from NUCLEAR FUSION, Vol.27, No.4 (1987)
Tritium Processing
PFC
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST Studies also Defined in Detail the
Test Sequence for major R & D Tasks in Non-Fusion Facilities
Example of Figures from NUCLEAR FUSION, Vol.27, No.4 (1987)
Solid Breeders
Liquid Breeders
The FNST community updated these plans in 2001.
The changes were modest.
The time line had to be shifted by ~ 20 years.
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST Studies Science-Based FNST Pathway to DEMO
FNST Testing in Fusion Facilities
Non-fusion
facilities
Preparatory R&D
Modeling and
experiments in
non-fusion facilities
• Basic property
measurement
• Understand
issues through
modeling and
single and
multiple-effect
experiments
None of the top level
technical issues can
be resolved before
testing in the fusion
environment
Scientific Feasibility
Engineering
Feasibility
Engineering
Development
Stage I
Stage II
Stage III
1 - 3 MW-y/m2
> 4 - 6 MW-y/m2
0.1 - 0.3 MW-y/m2
 0.5 MW/m2
burn > 200 s
Sub-Modules/Modules
• Establish scientific feasibility of
basic functions under prompt
responses and under the impact of
rapid property changes in early life
1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks
1-2 MW/m2
steady state or long burn
COT ~ 1-2 weeks
Modules (10-20m2 )
Modules/Sectors (20-30m2 )
• Establish engineering feasibility
of blankets/PFC/materials
(satisfy basic functions &
performance, up to 10 to 20% of
MTBF and of lifetime)
D
E
M
O
• RAMI: Failure modes, effects, and
rates and mean time to replace/fix
components and reliability growth
• Verify design and predict
availability of FNST components in
DEMO
• Details of requirements on wall load, energy fluence, plasma mode, etc. are
derived based on engineering scaling and described in several papers
• Other important requirements, e.g. surface heat flux, B also defined
• The stages are consecutive steps in scientific/technological development,
they can be carried out in one or more facilities
• Facility operation has to add other considerations, e.g. DD phase, availability
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
Why FNSF should be Low Fusion Power, Small Size, low Q
• The idea of FNSF emerged in the 1980’s from considering the following question:
 Should we combine the plasma physics mission with the FNST mission in one facility or
two separate facilities?
• The answer in FINESSE was TWO SEPARATE facilities:
One for plasma physics (ITER), and Another for FNST (FNSF)
Primary Reason
a. Plasma physics testing requires large fusion power (high Q/ignition) but short operating time.
b. FNST requires small fusion power but long operating time.
 Combining a and b results in extremely large tritium consumption (>300 kg) and highcost , high-risk device.
FNSF should be low fusion power, small size
•
•
•
•
•
To reduce risks associated with external T supply and internal breeding shortfall
Reduce cost (note Blanket/FW/ Divertor will fail and get replaced many times)
FNST key requirement 1-2 MW/m2 on 10-30 m2 test area
Cost/risk/benefit analysis lead to the conclusion that FNSF fusion power <150 MW
For Tokamak (including ST) this led to recommendation of:
– Low Q plasma (2-3) - and encourage minimum extrapolation in physics
– Normal conducting TF coil (to reduce inboard B/S thickness, also increase
maintainability e.g. demountable coils).
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNST studies over the past 25 years used rollback approach.
It was very useful. It provided foundation for moving forward
In the last 2 years, the FNST community started also using a roll-forward
approach in partnership with the broader community and facility designers
to explore FNSF options and the issues associated with the facility itself
Findings:
• Rolling forward reveals practical problems we must face today like
-- Vac Vessel
-- MTBF/MTTR
-- standard A, ST, other configuration?
-- level of advanced physics -- level of flexibility in device configuration
• Sensitivity to exact details of the DEMO becomes less important – Instead: we find out
we must confront the practical issue of how to do things for the first time – nuclear
components never before built, never before tested in the fusion nuclear environment.
• Debate about “how ambitious FNSF should be” becomes less important because WE
DO NOT KNOW what we will find in the fusion nuclear environment.
-- How many stages FNSF can do? Maybe one FNSF can do all 3 stages. Or, we may
need 2 or 3 consecutive FNSF facilities. (remember fission did 63!!)
-- What critical flaws may be found in initial operation of FNSF? Maybe we cannot get
past stage 1? e.g. MTBF too short, MTTR too long, cannot contain tritium?
-- Maybe we will get an early answer to “is tokamak a feasible option for power plant?”
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6
FNSF Strategy/Design for Breeding Blankets,
Structural Materials, PFC & Vacuum Vessel
Day 1 Design
 Vacuum vessel – low dose environment, proven materials and technology
 Inside the VV – all is “experimental.” Understanding failure modes, rates,
effects and component maintainability is a crucial FNSF mission.
 Structural material - reduced activation ferritic steel for in-vessel components
 Base breeding blankets - conservative operating parameters, ferritic steel,
10 dpa design life (acceptable projection, obtain confirming data ~10 dpa & 100 ppm He)
 Testing ports - well instrumented, higher performance blanket experiments
(also special test module for testing of materials specimens)
Upgrade Blanket (and PFC) Design, Bootstrap approach
 Extrapolate a factor of 2 (standard in fission, other development), 20 dpa, 200 appm He.
Then extrapolate next stage of 40 dpa…
 Conclusive results (real environment) for testing structural materials,
- no uncertainty in spectrum or other environmental effects
- prototypical response, e.g., gradients, materials interactions, joints, …
16
Suggestions/Recommendations
• We used the rollback approach for the last 25 years. Now we need to move
forward.
• Assign a group of FNST experts to summarize and update FNST studies as to
R&D required, and requirements on FNSF mission/major parameters, major
features
• Start “roll forward” process to identify the best option for FNSF
– Address practical issues of building FNSF “in-vessel” components of the same materials
and technologies that are to be tested.
– Evaluate issues of facility configuration, maintenance, failure modes and rates, physics
readiness (Quasi-steady state? Q ~ 2-3?). These issues are critical and they vary with
proposed FNSF facility. (e.g. standard A vs. ST)
– Address role and mission of initial phase DD operation in FNSF.
– Need a Mechanism/Process for comparing various options for FNSF facility
• Find a way to engage experts in RAMI in the fusion program and particularly in pathway
development assessment (experts should have experience in technology development and have
analytical capabilities). RAMI considerations can be a deciding factor in evaluating different
options for FNSF mission and designs and can be the “Achilles Heel” for fusion.
• Enhance fundamental FNST R&D now
– Such fundamental R&D does not strongly depend on variations in details of vision for
DEMO or pathway. Results from R&D will help us improve the vision and pathway.
M. Abdou FNST Studies Perspective FNST/PFC/Materials Mtg. Aug 2-6